Indium tin oxide (ITO) thin films are conventionally used as transparent electrically-conductive thin films, because of their excellent transparency. Among transparent electrically-conductive thin films for the above applications, for example, those for use in touch panels and the like are desired to have high resistance values, in view of position detection accuracy or power consumption. Transparent electrically-conductive thin films for the above applications are also desired to have satisfactory reliability in high-temperature, high-humidity environments (the smaller the rate of resistance value change, the higher the reliability). After formed, transparent electrically-conductive thin films may also be crystallized so as to have improved reliability.
However, conventional transparent electrically-conductive thin films using indium tin oxide thin films have low resistance values and insufficient reliability. The reliability can be improved by increasing a thickness of the transparent electrically-conductive thin film. However, such an increase in thickness can result in a reduction in transparency or resistance value and thus is not preferred. The reliability of the transparent electrically-conductive thin film can also be improved by increasing a content of tin oxide in the indium tin oxide thin film. However, too high tin oxide content can make the time for crystallization very long and thus is not preferred.
To solve the problems, it is proposed that an indium tin oxide thin film is doped with nitrogen (see Patent literature 1). Patent literature 1 discloses that in the nitrogen-containing transparent electrically-conductive thin film, a nitrogen content of 0.25% by weight or more based on the amount of indium tin oxide can be effective in improving the resistance value or reliability of the transparent electrically-conductive thin film. However, the transparent electrically-conductive thin film disclosed in Patent Literature 1 is amorphous, and crystallization thereof for a further improvement in the reliability requires a very long time.
Patent literature 1: Japanese Patent Application Laid-Open No. 04-308612